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Dr. Altdorfer: Microscopy of the spinal cord, proprioceptive and nociceptive reflexes

Dr. Altdorfer: Microscopy of the spinal cord, proprioceptive and nociceptive reflexes. Microscopy of the spinal cord. Dorsal horn: I-VI. Intermediate zone: VII., X. Ventral horn: VII-VIII-IX. Rexed I. Rexed II. III-IV. Rexed VII. Th9-L3. Rexed VII. Th1-L3. Rexed IX.

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Dr. Altdorfer: Microscopy of the spinal cord, proprioceptive and nociceptive reflexes

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  1. Dr. Altdorfer: Microscopy of the spinal cord, proprioceptive and nociceptive reflexes

  2. Microscopy of the spinal cord Dorsal horn: I-VI. Intermediate zone: VII., X. Ventral horn: VII-VIII-IX.

  3. Rexed I. Rexed II. III-IV. Rexed VII. Th9-L3 Rexed VII. Th1-L3 Rexed IX.

  4. Spinal reflexes(reflex: stimulus  response) • Stretch reflex (or monosynaptic, proprioceptive, myotatic) • Withdrawal reflex (or polisynaptic, nociceptive, flexor…) • Autonomous reflex (or vegetative) • Receptor • Sensory neuron • (Interneuron) • Effector neuron • Effector organ

  5. Spinal reflexes • Stretch reflex (or monosynaptic, proprioceptive, myotatic) • Withdrawal reflex (or polisynaptic, nociceptive) • Autonomous reflex (or vegetative) • Receptor • Sensory neuron • (Interneuron) • Effector neuron • Effector organ

  6. Proprioceptive reflex

  7. Proprioceptive reflex

  8. Proprioceptive reflex

  9. Proprioceptive reflex • Receptor: muscle spindle • Sensory neuron: in DRG - Aα /Ia/ fibres • (Interneuron) no! • Effector neuron: in vental horn, Aα motoneuron • Effector organ: motor end plate (Ach) Antigravitation muscles – to set the tone / posture / body position Receptor and effector in the same striated muscle!

  10. Proprioceptive reflexes Inhibitory interneuron

  11. Receptor: muscle spindle

  12. Muscle spindle

  13. Muscle spindle • intrafusal muscle fibers (nuclear bag fibers, nuclear chain fibers) • motor neurons - gamma motor neurons (which activate intrafusal fibers) • sensory nerve fibers - annulospiral sensory nerve endings (Type Ia sensory fibers) - flower spray sensory nerve endings (Type II sensory fibers)

  14. Masseter reflex (jaw jerk reflex)

  15. Proprioceptive reflex

  16. Spinal reflexes(reflex: stimulus  response) • Stretch reflex (or monosynaptic, proprioceptive, myotatic) • Withdrawal reflex (or polisynaptic, nociceptive, flexor…) • Autonomous reflex (or vegetative) • Receptor • Sensory neuron • (Interneuron) • Effector neuron • Effector organ

  17. Withdrawal reflex Contraction of ipsilateral flexor muscles, inhibition of ipsilateral extensor (anatgonist) muscle motoneurons (reciprocal innervation) + On the other limb: …  crossed flexor-extensor reflex

  18. Withdrawal reflex Withdrawal reflex (or polisynaptic, nociceptive, flexor…) Protection from harmful stimuli (noxa) Receptor and effector in different tissues / organs!

  19. Withdrawal reflex • Receptor: free nerve endings (in skin, mucosa) - nociceptors • Sensory neuron: in DRG. Aδ , C fibres (thin myelin sheath or unmyelinated) • Interneuron: at least 1 in dorsal horn! • Effector neuron: in vental horn, Aα motoneuron • Effector organ: motor end plate (Ach) • E.g.: cremaster-reflex, cornea-reflex, pharyngeal (gag) reflex

  20. Withdrawal reflex • (or polisynaptic, nociceptive, flexor…) • Smaller diameter (Aδ, C) fibres  slower • Multisynaptic  longer latency

  21. Withdrawal reflex

  22. Withrawal reflex

  23. Withrawal reflex

  24. Stretch reflex • (or monosynaptic, proprioceptive, myotatic) • Setting the tone / posture / body position • Antigravitation muscles • Receptor and effector in the same striated muscle! • Withdrawal reflex • (or polisynaptic, nociceptive, flexor) • Protection from harmful stimuli (noxa) • Physiological flexor muscles • Receptor and effector in different tissues / organs!

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